private HLDTreeNode FindLCA(HLDTreeNode p, HLDTreeNode q)
{
if (p.depth < q.depth)
{
var t = p;
p = q;
q = t;
}
if (p.segId == q.segId)
{
//on same segment tree
return(q);
}
var pa = segNodes[p.segId][0];
if (pa.depth >= q.depth)
{
return(FindLCA(pa.parent, q));
}
var qa = segNodes[q.segId][0];
if (qa.depth <= pa.depth)
{
return(FindLCA(pa.parent, qa.parent));
}
return(FindLCA(p, qa.parent));
}
private void BuildTree(List <int[]> edges)
{
var N = edges.Count;
var sortedEdges = new List <int[]> [N + 1];
for (int i = 0; i < N; i++)
{
if (sortedEdges[edges[i][0] - 1] == null)
{
sortedEdges[edges[i][0] - 1] = new List <int[]>();
}
sortedEdges[edges[i][0] - 1].Add(new int[2] {
edges[i][1], edges[i][2]
});
}
var nodeIdStack = new Stack <int>();
nodeIdStack.Push(0);
var parentStack = new Stack <HLDTreeNode>();
parentStack.Push(root);
while (nodeIdStack.Count > 0)
{
var id = nodeIdStack.Pop();
var parent = parentStack.Pop();
if (sortedEdges[id] == null)
{
//leaf
continue;
}
foreach (var edge in sortedEdges[id])
{
var node = new HLDTreeNode
{
id = edge[0] - 1,
parent = parent,
children = new List <HLDTreeNode>(),
value = edge[1],
depth = parent.depth + 1
};
nodes[edge[0] - 1] = node;
parent.children.Add(node);
parent.size++;
nodeIdStack.Push(edge[0] - 1);
parentStack.Push(node);
}
}
//Currently all size is the number of its direct children, update
UpdateSize(root);
}
private int GetMaxEdge(HLDTreeNode start, HLDTreeNode end)
{
if (start.segId != end.segId)
{
var max = segTrees[start.segId].GetCombine(0, start.segPos);
return(Math.Max(max, GetMaxEdge(segNodes[start.segId][0].parent, end)));
}
else
{
if (end.segPos == start.segPos)
{
return(int.MinValue);
}
else
{
return(segTrees[start.segId].GetCombine(start.segPos, end.segPos + 1));
}
}
}
public HLD(List <int[]> edges)
{
root = new HLDTreeNode()
{
id = 0,
parent = null,
children = new List <HLDTreeNode>(),
value = int.MinValue
};
segNodes.Add(new List <HLDTreeNode>()
{
root
});
nodes = new HLDTreeNode[edges.Count + 1];
nodes[0] = root;
BuildTree(edges);
HeavyLightDecomposition(root, 0);
CreateSegTrees();
}
private void UpdateSize(HLDTreeNode node)
{
if (node.children.Count > 0)
{
foreach (var child in node.children)
{
UpdateSize(child);
}
var t = 1;
foreach (var child in node.children)
{
t += child.size;
}
node.size = t;
}
else
{
node.size = 1;
}
}
private void HeavyLightDecomposition(HLDTreeNode node, int index)
{
if (node.children.Count == 0)
{
return;
}
HLDTreeNode maxchild = null;
var max = -1;
foreach (var child in node.children)
{
if (child.size > max)
{
maxchild = child;
max = child.size;
}
}
maxchild.segId = index;
maxchild.segPos = segNodes[index].Count;
segNodes[index].Add(maxchild);
HeavyLightDecomposition(maxchild, index);
foreach (var child in node.children)
{
if (child != maxchild)
{
var newIndex = segNodes.Count;
child.segId = newIndex;
child.segPos = 0;
segNodes.Add(new List <HLDTreeNode>()
{
child
});
HeavyLightDecomposition(child, newIndex);
}
}
}
